The surface of the membrane lining the structures within the nose may show an excessive amount of mucus. There may be a collection of mucopurulent exudate on the floor of the nasal passages. Occasionally one passage will be completely plugged with a mass of dirty, cheeselike material.
The postmortem findings usually are quite characteristic. Some individuals, however, will present changes that may be normal defects or are not differentiated enough to permit reaching a definite conclusion as to whether or not the animal is affected.
THE DIAGNOSIS of atrophic rhinitis may not appear to be difficult. When it is not suspected, however, the disease can be present in a herd for a year or two before it is recognized, because the various symptoms can easily be attributed to other causes. The sneezing may be thought to be due to inhalation of dust or particles of dry feed. The coughing could be considered as caused by the migration of larvae of intestinal worms. The bleeding could be considered insignificant in the mistaken belief that it may have been due to a ruptured blood vessel following injury or extreme exercise. A crooked nose could be thought of as having been due to injury, "bull nose" (or necrotic rhinitis), or the influence of a breed characteristic.
A postmortem examination, however, conducted on a few individuals that showed symptoms will confirm a herd diagnosis.
In most instances, to see within the nose, it is sufficient to make a cross section with a saw midway between the eyes and the end of the snout. For more detailed observations, the snout and face can be divided lengthwise down the midline and the nasal septum removed. This will reveal the nasal cavities in their entirety.
Although a herd diagnosis of atrophic rhinitis can be reached, the number of individual animals affected can only be approximated on the basis of clinical findings. In order to arrive at an individual diagnosis, a rhinoscopic examination may be conducted. That is done with the aid of an otoscope, a lighted instrument for examining the external ear. The instrument can be used with speculums of various sizes, depending on the size of the pig to be examined. When the attached speculum is inserted in the nostril, the light will reveal the anterior portion of the turbinates and nasal septum. Unfortunately the nasal structures cannot be seen completely or in the most desirable perspective; therefore there may be inaccuracies of diagnosis, particularly when the changes are not far advanced. This method is about 75 percent accurate.
A rhinoscopic examination cannot be conducted unless the animal is restrained properly. Several methods can be used: An anesthetic agent, a castrating trough with a crosspiece at one end, or a chute equipped with an adjustable stanchion or yoke to accommodate pigs of any size. The stanchion or yoke must be designed so that it is somewhat wider at the bottom than at the top to conform to the shape of the neck.
The X-ray can be employed in making a diagnosis on the individual live animal.
No SATISFACTORY TREATMENT has been devised for atrophic rhinitis. Adequate treatment cannot be evaluated until the causes are established. Because it appears doubtful that regeneration of atrophied parts occurs, any treatment must necessarily be directed towards its prevention or arrest in the early stages.
R. Gwatkins, P. J. G. Plummer, J. L. Byrne, and R. V. L. Walker, of the Animal Disease Research Institute, Canada, found experimentally that penicillin and streptomycin inhibited the infective agent or agents when added to the inoculum before being instilled into noses of susceptible pigs.
Gwatkins and Dzenis also found that the early use of streptomycin intranasally will reduce the number of pigs that develop atrophic rhinitis. T. L. Jones, also of the Ontario Veterinary College, reported that intramuscular injections of streptomycin administered three times during the first month after birth reduce the incidence of rhinitis but will not eliminate the disease.
CONTROL MEASURES Must proceed along generally recognized principles of disease control.
The most satisfactory method of control is to try to keep the disease out of a herd. Much can be accomplished by learning everything possible about conditions in the herd from which replacements are to be obtained.
A more drastic method is to dispose of the affected herd. Thorough cleaning and disinfection of the buildings and equipment should follow. It would be well to renovate the lots by filling in wallows and by providing drainage in the low, boggy areas. Replacements from disease-free herds can be made after several months. The disadvantages of such a program are obvious, however, especially when valuable breeding animals are implicated or when it is doubtful that healthy replacements can be obtained.
A third method involves the selection within the herd of normal-appearing pigs for breeding purposes and the elimination of those that are obviously affected. Such a program could be improved by using the rhinoscope to aid in the selection and rejection of the pigs.
At the Agricultural Research Center we found that we could minimize the incidence of atrophic rhinitis by raising rhinoscopically negative weanlings to maturity in an isolation area under conditions of litter segregation and raising a second generation of pigs under the same conditions.
A fourth method offers a means of obtaining swine free of atrophic rhinitis but has practical limitations. This method consists of removing the baby pigs from the dam by hysterectomy or Caesarean section, or catching them in sterile bags or on sterile cloth as they are born and removing them 24 hours after birth. In all instances the baby pigs must be hand raised under isolated conditions. Such procedures can be used when it is necessary to obtain valuable breed strains free of the disease and when adequate facilities and sufficient help for the sanitary care and management of the baby pigs are available.
RICHARD D. SHUMAN is a veterinarian in the Bacterial and Mycotic Diseases Section of the Animal Disease and Parasite Research Branch.
JOHN S. ANDREWS is a parasitologist in the Helminth Parasite Section of the Animal Disease and Parasite Research Branch at Beltsville. He majored in parasitology at Purdue University.
F. L. EARL is a veterinarian in the Viral and Rickettsia) Diseases Section of Agricultural Research Service. Following graduation from Michigan State University in 1947, Dr. Earl was employed by the State veterinarian's office in Missouri investigate pullorum and Newcastle disease. In 1948 he joined the Department of Agriculture as station veterinarian in Beltsville.